Week 7 Fatty Acid Sythesis Flashcards
Why synthesise fatty acids?
We need them!
-Energy storage
Key constituents of cell membrane
Extracellular & intracellular messengers
Hormones
Co-factors
Transporters
Pigments
Detergents
Acetyl-
CoA – centre of the universe?
For fatty acids it is!
Free fatty acids >b oxidation > acetyl CoA
^
Lipolysis ^
^. | deamination
Triglyceride |. & oxidation
Protein —— proteolysis > amino acids
Acetyl CoA = sterols and fatty acids, TCA cycle, ketone bodies and protein acetylation
But we
actually need malonyl-CoA
Need to add a reactive group onto it = bicarbonate
We lengthen chain by a single carbon = malonyl- CoA
Limited step
Actyel CoA is a key enzyme
Acetyl-CoA carboxylase
1 biotin carrier protien
2- biotin carboxylate religion
Transcarboxalse region
2 reactions taking place
ATP dependent reaction
Carrier protien move activated carbon dioxide to move across
Make carbon dioxide available to acetyl CoA = can come into close proximity of carbon dioxide are able to react to produce malonyl CoA
Biotin > transcarboxyalse region
Fatty acid synthesis
Long chain
fatty acids assembled by:
4-step repeating sequence
Catalysed by fatty acid synthase
Polypeptide homodimer
Contains all 7 active sites required for synthesis of palmitate (16:0)
Only need 1 enzyme = fatty acid synthase
Addition of 2 carbons, needs 4 steps
Alpha carbon is closest to actyel group
Need to reduce keto group to most simple version - only hydro carbons
3rd reaction is removing alcohol condensation reaction producing water (dehydrate ir )
Start of producing fatty acid ,
Condensation to acetyl group , limitation of CO2 , extending acyl chain by 2 carbons
Condensed and reduced
Loss of co2
Alpha carbon and beta carbon (keto) and reduced into alcohol by NADh by adding h
Next Elimate water producing double bond
4th - donates proton reducing unsaturated double bond producing saturated fatty acteyl CoA
7 rounds
Fatty acid Synthesis
1) Fatty acid synthase complex charged with acetyl and malonyl group is condensed ( removal of co2 )
2) reduction of b-keto group ( NADPH + H+= NADP+)
3) Dehydration ( removal of H20 )
4) reduction of double bond
NADPH + H+ = NADP+
5) translocation of butyryl group to Cys on B-ketoacyl synthase
6) recharging of ACP with another malonyl group
Location and regulation of fatty acid synthesis
Animal cells
Cytosol =NADPH PRODUCTION
Isoprenoid and sterol synthesis (early stages)
Fatty acid synthesis
Plant cells
Chloroplasts
NADPH,ATP production
Fatty acid synthesis
Peroxisomes
Fatty acid oxidation ——> H2O2
Catalase peroxidase
H202-> h20
REGULATION OF FATTY ACID SYNTHESIS
Citrate
|
v. Citrate lyase
Acetyl CoA
|
|. X. Glucagon, epinephrine, trigger phosphorylation/
|. Inactivation
Malonyl- CoA
v
Palmitoyl
